Protective headguard

ABSTRACT

Protective headguard comprising overlapped inner and outer layers attached so as to permit frictional sliding of at least one area of the outer layer over the inner layer.

[0001] This application claims the benefit of United States ProvisionalApplication No. 60/445,153, filed Feb. 5, 2003.

FIELD OF INVENTION

[0002] The present invention generally relates to protective headgear.Specifically, it relates to protective headgear intended to reduceangular acceleration of the human brain caused by an impact to theprotective headgear.

BACKGROUND OF THE INVENTION

[0003] The prior art contains many examples of protective headgear orhelmets intended to attenuate shock directed at the head. Protectiveheadgear is used in many human sports and activities such as Americanfootball, Australian rules football, martial arts, equestrian sports,wrestling, cycling, lacrosse, baseball, hockey, inline skating,skateboarding, skiing, snowboarding, soccer, rock climbing andwhitewater canoeing or kayaking. Protective headgear is also used inwork activities such as construction, the military and firefighting.

[0004] Headgear is generally designed to protect the head from at leastone of three kinds of impact. First, protective headgear may be intendedto protect the wearer from penetrating objects. This is particularlytrue with military headgear. Second, headgear may be designed to protectthe wearer from contact loading, i.e., loading at the point of impact.An injury from contact loading might be a skull fracture.

[0005] Third, headgear may be intended to protect the wearer frominertial loading, i.e., acceleration or deceleration of the brain froman impact to the head. There are two kinds of head acceleration that canoccur in an impact. Acceleration of the head in a plane directed at thehead's center of gravity is called linear or translational acceleration.Acceleration along an arc is called angular or rotational acceleration.Given the structure of the brain and skull, and the way they respond toforces, most biomechanical and medical research indicates that angular,rather than linear, acceleration causes relatively greater damage to thebrain. See, e.g., Holbourn, A. H. S., “Mechanics of Head Injuries,” TheLancet, 2, 438-441 (1943); Ommaya, A. K. and Gennarelli, T. A.,“Cerebral Concussion and Traumatic Unconsciousness: Correlations ofExperimental and Clinical Observations on Blunt Head Injuries,” Brain,97, 633-654 (1974). It has been demonstrated that padding can reduceangular acceleration of the head. See, Sances, A. and Kumaresan, S.,“Padding in Child Restraint and Roll Bar Systems for Head InjuryReduction,” published at http://www.ataassociates.com/sances/index.html.However, the prior art contains few examples of padding or shockattenuation systems intended to manage changes in angular acceleration.

[0006] This lack of systems intended to manage changes in angularacceleration is significant. In many instances the materials or systemsthat best manage or modulate linear forces may not best manage ormodulate angular forces. Moreover, since the head of a wearer ofprotective headgear may be subjected to both linear and angularacceleration in response to an impact, it is important that devices bedeveloped that protect wearers from both linear and angular impactforces.

[0007] The few examples of materials and systems that do seek to protectwearers from linear and angular forces can be grouped as follows. Thefirst group of protective headgear devices includes those deviceswherein the padding is formed or constructed in a way to absorb angularforces. Such technologies take a material with certain properties andimprove its ability to respond to shearing forces by shaping or formingthe material in a certain way.

[0008] For example, U.S. Pat. No. 6,397,399 to Lampe et al. fits withinthis first category. The Lampe (399) patent discloses a headguard foruse in sports such as soccer. The headguard has padding consisting ofpillows or “nubbins” covering at least a portion of the forehead of thewearer. When angular forces are directed at the surface of theheadguard, the nubbins bend allowing the exterior surface of theheadguard to shift in the direction of the. angular force. This shiftingmay help modulate the angular acceleration of the head.

[0009] There may be practical limitations on the height of the pillowsor nubbins for protective headgear. Given this, they may be best suitedfor applications where the angular forces are limited.

[0010] Another group of technologies includes devices wherein a materialof a lower shear modulus (i.e., an elastic body) is positioned inheadgear between a shell (i.e., a rigid outer layer) and a liner. Thiselastic body lowers the overall shear modulus of the protective layers.U.S. patent application, Pub. No. US 2001/0032351 to Nakayama et al., isan example of this. The Nakayama Application discloses a helmet with arigid shell and inner liner. An elastic body, such as a gel, ispositioned between the shell and the inner liner and “stuck” to theinterior side of the shell and the exterior side of the inner liner. Theelastic body would permit the shell to shift in relation to the linerwhen angular forces are directed at the helmeted head. To permit theshell to shift in all directions, the Nakayama patent discloses aspherical shaped shell and liner.

[0011] The device disclosed in the Nakayama Application has limitations.First, with a rigid shell or a rigid liner, rotation of that shell inrelation to the liner can only effectively occur if both the shell andthe liner are substantially spherical in shape. The head, however, isnot spherically shaped. To create an inner liner with a sphericallyshaped outer surface would require adding substantial bulk to the liner.For many applications, therefore, the device contemplated by theNakayama Application may be impractical. Second, rotation will belimited by the elasticity of the elastic body. Third, the resistance toshearing may increase as the elastic body is stretched. While this maybe suitable for some applications, in others it may be desirable to havea more constant rate of resistance.

[0012] A final group of headgear intended to modulate angularacceleration of the head includes devices where the protective headgearas a unit can move on the surface of the head to attenuate angularforces. U.S. Pat. No. 6,247,181 to Hirsch et al. discloses a bandanatype headband with foam encased by fabric. The non-rigidity of thedevice itself allows the inner surface of the headgear to move acrossthe head in response to angular forces.

[0013] The capability of headgear to move in relation to the surface ofthe head is not unique to the device disclosed in the Hirsch Patent. Anyprotective headgear that fits less snugly or that has the capacity todeform and shift as a unit in response to an impact could perform thesame function. However, the capacity for such a device to modulateangular forces may be difficult to predict or control since head shapes,moisture on the surface of the head, and hair may all affect thiscapacity.

[0014] There is a need therefore for a device that can respond to andhelp protect the head from relatively high levels of angular forces;that can be incorporated into a piece of headgear of less bulk andweight; and that could consistently provide protection to the head fromangular forces.

SUMMARY OF THE INVENTION

[0015] Generally, the present invention relates to improvements to aheadguard for athletes. A first aspect of the invention is a headguardcomprising overlapped inner and outer layers attached so as to permitfrictional sliding of at least one area of the outer layer over theinner layer.

[0016] A second aspect of the invention is a headguard comprisingoverlapped inner, intermediate and outer layers attached so as to permitfrictional sliding of at least one area of the outer layer over theintermediate layer.

[0017] A third embodiment of the invention is a headguard comprising (i)overlapped inner and outer layers, and (ii) a flowable materialintermediate the layers, wherein (iii) the inner and outer layers areattached so as to permit sliding of at least one area of the outer layerrelative to the inner layer subject to drag exerted by the flowablematerial.

[0018] Objects and advantages of this invention include:

[0019] Protective headgear that reduces or modulates angularacceleration of the head by reducing or modulating rotational forcesacting upon the head.

[0020] Protective headgear that can consistently reduce or modulaterelatively high levels of rotational forces acting upon the head.

[0021] Protective headgear that not only reduces or modulates rotationalforces but also modulates linear forces.

[0022] Protective headgear that is relatively lightweight.

[0023] Protective headgear that reduces or modulates rotational forceswith at least two layers that at least at certain locations are notconnected and that can slide in relation to one another at or near thoseunconnected locations.

[0024] Protective headgear where the ease with which the two layers canslide in relation to one another is regulated at the interface of thosetwo layers. Examples of such regulating materials include:

[0025] Introducing fluids of either lower or higher viscosity betweenthe layers to adjust the ease with which the layers can slide inrelation to each other.

[0026] Introducing a gas between the layers to adjust the ease withwhich the layers can slide in relation to each other.

[0027] Inserting particles between the layers to adjust the ease withwhich the layers can slide in relation to each other.

[0028] Providing the layers with interfacing surfaces of greater orlesser smoothness to adjust the ease with which the layers can slide inrelation to each other.

[0029] Inserting a third layer of material, such as a film interposedbetween the layers, to adjust the ease with which the layers can slidein relation to each other.

[0030] Modifying the texture of the interfacing surfaces of the outerand inner layers to adjust the ease with which the layers can slide inrelation to each other.

[0031] Affixing rougher or smoother materials to one or both of theinterfacing surfaces to adjust the ease with which the layers can slidein relation to each other.

[0032] Protective headgear in which the interfacing surfaces of theinner and outer layers may be but do not have to be spherical.

[0033] Protective headgear in which the sliding of the layers as theresult of an impact permanently deforms the protective headgear.

[0034] Protective headgear in which the sliding of the layers as theresult of an impact does not permanently deform the protective headgear.Examples of means for achieving such a recoverable repositioning of thelayers include:

[0035] Construction of one or both layers from an elastic material.

[0036] Use of elasticity anchors (where the layers are connected).

[0037] Manual realignment of the layers to their original orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The invention may be more completely understood in considerationof the following detailed description of various embodiments of theinvention in connection with the accompanying drawings.

[0039]FIG. 1 is a side elevation view of a first embodiment of theexternal configuration of the headgear worn by a wearer.

[0040]FIG. 2 is a side elevation view of a second embodiment of theexternal configuration of the headgear worn by a wearer.

[0041]FIG. 3 is a cross-sectional side view of one configuration of thelayers used to form the headgear.

[0042]FIG. 4 is a cross-sectional side view of headgear having theexternal configuration of FIG. 1 with a deformable outer layer afterlocalized deformation of a portion of the outer layer caused byapplication of an angular force upon the headgear.

[0043]FIG. 5 is a cross-sectional side view of the headgear having theexternal configuration of FIG. 1 with a rigid outer layer after slidingof the outer layer relative to the inner layer caused by application ofan angular force upon the headgear.

[0044]FIG. 6 is a cross-sectional side view of the headgear having theexternal configuration of FIG. 1 with an interface layer between theinner and outer layers after deformation of the outer layer relative tothe inner layer caused by application of an angular force upon theheadgear.

[0045]FIG. 7 is a side elevation view of the headgear having theexternal configuration of FIG. 2 with a flexible outer layer aftersliding of the front portion of the outer layer relative to the innerlayer caused by application of an angular force upon the headgear.

[0046]FIG. 8 is a side elevation view of the headgear having theexternal configuration of FIG. 2 with a rigid outer layer after slidingof the outer layer relative to the inner layer caused by application ofan angular force upon the headgear.

[0047]FIG. 9 is an exploded cross-sectional view of an embodiment of theinner and outer layers of the headgear with nodules on the interfacingsurfaces of the layers.

[0048]FIG. 10 is a perspective view of the inner layer shown in FIG. 9.

[0049]FIG. 11 is an exploded cross-sectional view of another embodimentof the inner and outer layers of the headgear with “hair-like”projections on the interfacing surfaces of the layers.

[0050]FIG. 12 is a perspective view of the inner layer shown in FIG. 11.

[0051]FIG. 13 is an exploded cross-sectional view of yet anotherembodiment of the inner and outer layers of the headgear with sphericalparticles on the interfacing surface of the inner layer.

[0052]FIG. 14 is a perspective view of the inner layer shown in FIG. 13.

[0053]FIG. 15 is an exploded cross-sectional view of still anotherembodiment of the inner and outers of the headgear with irregular-shapedparticles on the interfacing surface of the inner layer.

[0054]FIG. 16 is an exploded cross-sectional view of a final embodimentof the inner and outer layers of the headgear with an intermediate filmbetween the inner and outer layers.

DETAILED DESCRIPTION OF THE INVENTION INCLUDING A BEST MODE Nomenclature

[0055]100 head of person

[0056]101 headgear

[0057]103 forehead area

[0058]104 top of head

[0059]105 temples

[0060]106 ears

[0061]107 back of head

[0062]108 chinstrap

[0063]109 headband embodiment

[0064]121 rivet

[0065]200 head of person

[0066]201 headgear

[0067]212 comfort liner

[0068]213 inner layer

[0069]214 outer layer

[0070]215 interface

[0071]300 head of person

[0072]301 full coverage embodiment

[0073]303 forehead area

[0074]304 top of the head

[0075]312 comfort liner

[0076]313 inner layer

[0077]314 outer layer

[0078]315 interface

[0079]320 force

[0080]321 rivet

[0081]322 crumpled area of outer layer

[0082]323 areas remote from impact

[0083]325 sliding

[0084]328 edges of headgear

[0085]400 head of person

[0086]403 forehead area

[0087]406 ears

[0088]407 back of head

[0089]409 headband embodiment

[0090]413 inner layer

[0091]414 outer layer

[0092]415 interface

[0093]420 force

[0094]421 rivet

[0095]425 sliding

[0096]426 deformed area

[0097]427 rotation

[0098]513 inner layer

[0099]514 outer layer

[0100]515 interface

[0101]530 nodules

[0102]531 hair-like projections

[0103]532 spherical particles

[0104]533 non-spherical particles

[0105]534 film

[0106] Construction and Use

[0107]FIGS. 1 and 2 are examples of protective headgear 101 and 109,respectively. FIG. 1 shows the head 100 of a person wearing a unitarypiece of headgear 101 that covers the forehead area 103, the top of thehead 104, the temples 105, the ears 106, and the back of the head 107.As shown in FIG. 1, an optional chinstrap 108 could help secure theheadgear 101 to the head 100. FIG. shows a protective headband 109 thatprovides a band of coverage from the forehead area 103, over the temples105, to the back of the head 107.

[0108] The purpose of these illustrations is not to exhaust the possibleheadgear configurations that could employ embodiments of the invention.Rather, the purpose is to show the many different kinds of headgearconfigurations could embody the invention.

[0109]FIG. 3 is a cross-section of the layers of one embodiment of theheadgear 201 that could be present in any of the headgear embodiments,including the headgear embodiment 101 of FIG. 1 and the headbandembodiment 109 of FIG. 2. Referring to FIG. 3, the invention can includean optional comfort liner 212 next to the head 200 of the wearer. Thecomfort liner 212 could be, for example, a lower density, open-cell foammaterial that easily conforms to the head 200 and provides sweat andheat management characteristics. The comfort liner 212 could also bemade up of multiple open-cell foam pads (not shown). Many other kinds ofmaterial and configurations of material could be employed in a comfortliner 212.

[0110] The next layer could be the inner layer 213. The inner layer 213could consist of padding intended to absorb some of the load of theimpact, especially those with a linear component. It could have plasticor elastic characteristics, depending on the application. Plasticmaterials have been found to be more suitable for protection fromsingle, high-energy impacts. Materials with plastic characteristics thatare commonly used in protective headgear include ones made frompolystyrene, polypropylene, or polyurethane. An elastic material shouldbe more suitable for multiple, lower energy impacts where the headgear101 or 109 needs to be re-used. A common material for such applicationswould be foams such as cross-linked polyethylene. However, other foams,gels, fluids, or gases sealed in film (not shown) would be suitable formany applications.

[0111] The outer layer 214 could also be the exterior layer or theshell. If the outer layer 214 were to act as a shell, it could be madeof a rigid or semi-rigid material that distributes the load from animpact over a greater surface area of the inner layer 213. Suitablerigid or semi-rigid materials include polycarbonate,acrylonitrile-butadiene-Styrene (ABS), or fiberglass reinforced plastic(FRP). Materials suitable for forming a less rigid outer layer 214include specifically, but not exclusively, foam, fabric or impregnatedfabric.

[0112] The outer layer 214 (especially for linear impacts) may performmore of a load distribution function while the inner layer 213 mayperform more of a load absorption function. These functional roles,however, are not essential to the invention. For example, it may bedesirable in certain circumstances to have both the inner layer 213 andthe outer layer 214 perform a load distribution function with a thirdlayer (not shown) performing a load absorption function. In such aninstance, both the inner layer 213 and outer layer 214 could be made ofthe same rigid or semi-rigid materials described above. Alternatively,both the inner layer 213 and outer layer 214 could perform loadabsorption functions. In this case both layers 213 and 214 could be madeof the materials intended for energy absorption described above.

[0113] The inner layer 213 and outer layer 214 need not be innermost oroutermost layer respectively. The inner layer 213 and outer layer 214could be the only two layers in the headgear 201, or they could be twoof many layers. Additionally, the inner layer 213 and outer layer 214maybe composed of sub-layers. The descriptive terms inner and outer simplyestablish the relationship between two layers, with the inner layer 213positioned closer to the head 100, 200, 300, 400 than the outer layer214.

[0114] Referring to FIG. 3, the inner layer 213 cooperates with theouter layer 214 at the layer interface 215 defined by the exteriorsurface (unnumbered) of the inner layer 213 and the interior surface(unnumbered) of the outer layer 214.

[0115] At least at certain points at the interface 215, the inner layer213 and outer layer 214 are not connected to each other. Thus, when theexterior surface (unnumbered) of the outer layer 214 encounters anoblique force, such as forces 320 and 420 shown in FIGS. 4-8, theexterior surface (unnumbered) of the inner layer 213 and the interiorsurface (unnumbered) of the outer layer 214 will slide in relation toone another. At other points the inner layer 213 and outer layer 214 areconnected. These connection points are generically referred to herein asanchor points.

[0116]FIG. 4 depicts one embodiment of the invention subjected to anoblique force 320 having an angular vector (not separately shown). Theheadgear 301 in this embodiment covers the top of the head 304 and couldbe the same as the one shown in FIG. 1. In addition, the embodiment ofthe headgear 301 shown in FIG. 4 could have the same layers as thosedepicted in FIG. 3, (i.e., an outer layer 314, an inner layer 313, aninterface 315, and a comfort liner 312). The headgear 301 of theembodiment shown in FIG. 4 includes a rivet 321 attaching the innerlayer 313 and the outer layer 314 to each other at a single anchorpoint. Many other kinds of fasteners suitable for use in forming ananchor point are known to those skilled in the art, includingspecifically but not exclusively, sewn seams, adhesives and heatwelding.

[0117] The location of the anchor points could be varied. By way ofexample, FIG. 2 shows an alternative location for the anchor pointswherein rivets 121 are located on opposite the sides of the headgear 109just above the ears 106. Other anchor point locations might also bedesirable.

[0118] As shown in FIG. 4, the outer layer 314 may be formed of amaterial which is relatively non-rigid and therefore could be deformedwhen subjected to an oblique force 320 as evidenced by the crumpled area322 over the forehead 303 of a wearer. Crumpling of the outer layer 314is particularly desired when the inner layer 313 and outer layer 314 areanchored with a fastener, such as rivet 321, which is not elastic. Suchcrumpling allows the interior surface (unnumbered) of the outer layer314 to slide 325 in relation to the exterior surface (unnumbered) of theinner layer 313 even though the fastener (e.g., rivet 321) rigidlyattaches the inner layer 313 and the outer layer 314 at the anchorpoints.

[0119]FIG. 5 shows an embodiment of headgear 301 similar to the headgear301 shown in FIG. 4 subjected to an oblique force 320. The outer layer314 on the headgear 301 depicted in FIG. 5 is more rigid than the outerlayer 314 on the headgear 301 depicted in FIG. 4. Hence, the outer layer314 does not crumple when subjected to an oblique force 320. Rather, anelastic rivet 321 is employed at the anchor point, allowing the rivet321 to stretch and thereby allow the interior surface (unnumbered) ofthe outer layer 314 to slide 325 in relation to the exterior surface(unnumbered) of the inner layer 313 proximate the point of impact(unnumbered), even though the outer layer 314 is not appreciablydeformed by the oblique force 320. The outer layer 314 may be lifted offthe inner layer 313 at areas remote from the point of impact, such asrepresented by arrows 323 in FIG. 5.

[0120]FIG. 7 shows another embodiment of the invention in the form of aheadband 409. The headband 409 is represented as subjected to an obliqueforce 420. In this embodiment of the invention, the inner layer 413 andouter layer 414 are attached to each other at two laterally alignedanchor points by rivets 421 positioned just above each ear 406. Theouter layer 414 depicted in this embodiment is constructed of arelatively non-rigid material which will deform when subjected to anoblique force 420 as evidenced by the deformed area 426. The inner layer413 and outer layer 414 may be securely attached to one another, such asby an adhesive (not shown); over that portion (unnumbered) of theheadband 409 covering the back 407 of the head 400 to ensure thatdeformation occurs about the anchor points. Deformation about the anchorpoints causes the interior surface (unnumbered) of the outer layer 414to slide 425 in relation to the exterior surface (unnumbered) of theinner layer 313 only on that portion of the headband 409 covering theforehead area 403.

[0121] Referring to FIG. 8, the headband 409 may alternatively beconstructed without attaching the inner layer 413 and the outer layer414 at the back 407 of the head 400. Such an embodiment permits theentire outer layer 414 to rotate 427 as a unit about the rivets 421,resulting in sliding 425 of the front (unnumbered) and back (unnumbered)portions the interior surface (unnumbered) of the outer layer 415 overthe exterior surface (unnumbered) of the inner layer 413. The amount ofrotation 427 can be controlled by controlling the tightness of therivets 421.

[0122] Referring to FIG. 6, at least a portion of the interface 315 mayoptionally be sealed, such as by fusing the inner layer 313 and theouter layer 314 along the edges 328 and the interface 315 filled with aflowable material (unnumbered) such as solid particulates, liquid,gel orgas. When such a “filled” headgear 301 is subjected to an oblique force320, the interior surface (unnumbered) of the outer layer 314 will slidein relation to the exterior surface (unnumbered) of the inner layer 313by deformation of the inner layer 313 and/or the outer layer 314,thereby causing the fluid to flow within the sealed interface 315 suchas represented in FIG. 6. The thickness of the filled interface 315 maybe selected as necessary to achieve the desired effect, with a thicknessof just a few thousandths of an inch suitable for many applications. Theflow properties of the fluid retained within the sealed interface 315will affect the ease or difficulty with which the outer layer 314 willslide in relation to the exterior surface (unnumbered) of the innerlayer 313. For example, a high viscosity fluid might inhibit sliding,while a low viscosity fluid might facilitate sliding.

[0123] Particles (not shown) may optionally be suspended in the fluidretained within the sealed interface 315 to achieve a desired flowcharacteristic. When particles are incorporated into the fluid, thefluid preferably has a higher viscosity for purposes of facilitatinglong-term suspension of the particles in the fluid.

[0124] The ease or difficulty with which the interior surface(unnumbered) of the outer layer 214, 314, 414, 514 slides relative tothe exterior surface (unnumbered) of the inner layer 213, 313, 413, 513(hereinafter “slide control”) can be controlled in any number of ways.One variable which can be altered to effect slide control is therigidity of the inner layer 213, 313, 413, 513 and/or the outer layer214, 314, 414, 514. Another is the elasticity of the mechanism attachingthe layers at each anchor point.

[0125] Another variable which can be altered to effect slide control isthe frictional properties at the interface 215, 315, 415, 515 betweenthe inner layer 213, 313, 413, 513 and/or the outer layer 214, 314, 414,514. Several specific means for effecting a specific frictional propertyat the interface 215, 315, 415, 515 are shown in FIGS. 9-16. FIGS. 9 and10 show nodules 530 on the interior surface (unnumbered) of the outerlayer 514 and the exterior surface (unnumbered) of the inner layer 513.FIGS. 11 and 12 show hair-like projections 531 (e.g., felt) on theinterior surface (unnumbered) of the outer layer 514 and the exteriorsurface (unnumbered) of the inner layer 513. FIGS. 13 and 14 showspherical particles 532 on the exterior surface (unnumbered) of theinner layer 513. FIG. 15 shows irregular shaped particles 533 on theexterior surface (unnumbered) of the inner layer 513. FIG. 16 shows anintermediate film 534 positioned between the interior surface(unnumbered) of the outer layer 514 and the exterior surface(unnumbered) of the inner layer 513. Other embodiments would also beknown to those skilled in the art.

[0126] An additional advantage recognized with the hair-like projections531 and the nodules 530 is the ability of such features to absorb anoblique force by toppling or collapsing when subjected to such a force.

[0127] The present invention should not be considered limited to theparticular examples described above, but rather should be understood tocover all aspects of the invention as fairly set out in the claimsarising from this application. For example, while suitable sizes,materials, fasteners, and the like have been disclosed in the abovediscussion, it should be appreciated that these are provided by way ofexample and not of limitation as a number of other sizes, materials,fasteners, and so forth may be used without departing from theinvention. Various modifications as well as numerous structures to whichthe present invention maybe applicable will be readily apparent to thoseof skill in the art to which the present invention is directed uponreview of the present specifications. The claims which arise from thisapplication are intended to cover such modifications and structures.

We claim:
 1. A protective headguard, comprising overlapped inner andouter layers attached so as to permit frictional sliding of at least onearea of the outer layer over the inner layer.
 2. A protective headguard,comprising overlapped inner, intermediate and outer layers attached soas to permit frictional sliding of at least one area of the outer layerover the intermediate layer.
 3. A protective headguard, comprising (i)overlapped inner and outer layers, and (ii) a flowable materialintermediate the layers, wherein (iii) the inner and outer layers areattached so as to permit sliding of at least one area of the outer layerrelative to the inner layer subject to drag exerted by the flowablematerial.
 4. The protective headguard of claim 3 wherein the flowablematerial is solid particulates.
 5. The protective headguard of claim 3wherein the flowable material is a gel.
 6. The protective headguard ofclaim 3 wherein the flowable material is a liquid.
 7. The protectiveheadguard of claim 3 wherein the flowable material is a gas.
 8. Theprotective headguard of claim 1 wherein the inner and outer layers arebiased towards a standard position relative to one another.
 9. Theprotective headguard of claim 2 wherein the inner and outer layers arebiased towards a standard position relative to one another.
 10. Theprotective headguard of claim 3 wherein the inner and outer layers arebiased towards a standard position relative to one another.
 11. Theprotective headguard of claim 1 wherein the inner and outer layers areattached by elastic material.
 12. The protective headguard of claim 2wherein the inner and outer layers are attached by elastic material. 13.The protective headguard of claim 3 wherein the inner and outer layersare attached by elastic material.
 14. The protective headguard of claim1 wherein the inner layer is elastic.
 15. The protective headguard ofclaim 1 wherein the inner layer is inelastic.
 16. The protectiveheadguard of claim 1 wherein the outer layer is elastic.
 17. Theprotective headguard of claim 1 wherein the outer layer is inelastic.18. The protective headguard of claim 2 wherein the inner layer iselastic.
 19. The protective headguard of claim 2 wherein the inner layeris inelastic.
 20. The protective headguard of claim 2 wherein the outerlayer is elastic.
 21. The protective headguard of claim 2 wherein theouter layer is inelastic.
 22. The protective headguard of claim 1wherein the inner and outer layers each have an interfacing majorsurface and at least one of the interfacing surfaces has a roughtexture.